Place grated carrot and thinly sliced purple cabbage in a bowl with rice vinegar and salt. Toss gently. Let the mixture marinate, tossing occasionally, at least 10 minutes.
Bring a pot of salted water to boil. Cook soba noodles until al dente, about 4 minutes. Drain the noodles, then return them to the pot (off the heat). Stir in thinly sliced green onions, sesame seeds, soy sauce, and olive oil. Set aside.
To assemble lettuce wraps, spread a dollop of hummus over the center of a lettuce leaf. Top with small handful of soba noodles, then the carrot-cabbage mixture.
Sprinkle lightly with additional sesame seeds, salt, and pepper if desired.